Conventionally, a sheet-binding device or the like for applying adhesive to the back of a bundle of printed sheets and binding the sheets has an adhesive coating device provided with an adhesive reservoir for storing hot-melt adhesive and a coating roller disposed so that part thereof is immersed in the adhesive stored in the adhesive reservoir and so that the roller is journaled to be rotatable in the adhesive reservoir. The above-mentioned device, having been used in the mainstream, is provided with a heater in the adhesive reservoir so that the heater heats the adhesive to melt the adhesive.
However, in such indirect heating means as that uses the above-mentioned heater, the efficiency of heat transfer is low; three steps of heat transfer, from the heater to the adhesive reservoir, from the adhesive reservoir to the adhesive and from the adhesive to the coating roller, are required to sufficiently heat the coating roller, which serves as a member for directly applying the adhesive to the back of the bundle of sheets, to a predetermined temperature. Hence, it takes a long time until a standby state is attained, and it is difficult to accurately control the final temperature of the coating roller from the heater serving as a heat source. In addition, since the roller serving as a secondary heating member is required to be capable of carrying out heat transfer and to have a volume capable of sufficiently storing heat, it is necessary to increase the volume of the roller; as a result, the whole device becomes larger in size. Therefore, the atmospheric exposure area of the adhesive in the adhesive reservoir is required to be increased, causing problems of bad-smelling and the like.
Furthermore, in consideration of the efficiency of heat transfer, it is ideal that the coating roller can be heated directly and that the adhesive reservoir can be heated subordinately; this can make temperature control easy. This type of device is available as a device wherein, in addition to the heating of the adhesive reservoir using a heater, the coating roller is configured so as to be hollow and a halogen lamp is embedded therein.
However, in this type of device, the configuration of the coating roller itself becomes massive, resulting in making the whole device larger in size; in addition, since the coating roller is structured to rotate around its shaft, there is a problem of wire processing. Furthermore, if adhesive attaches to the halogen lamp, this may cause breakage; therefore, it is necessary to use a structure wherein the halogen heater is replaceable and to provide a seal for preventing the adhesive from entering the open area provided in the coating roller.